I also would never wash a top, for the reasons mentioned above. I've seen what happens (I work in a LQS) Yikes!
Many years ago, when I could still crawl on the floor, I basted a quilt on the floor, left it overnight, and found the next morning that my cat had urinated right smack-dab in the middle of it! I sprinkled it with baking soda and let it dry, then brushed it off. It still smelled somewhat, but not as bad, and I proceeded to quilt it. When it was done, I washed it, and the smell and stain disappeared.